The present disclosure relates to subterranean operations and, more particularly, to systems and methods for monitoring and characterizing well bores and fluids in a subterranean formation.
Performance of subterranean operations entails various steps, each using a number of devices. Many subterranean operations entail introducing one or more fluids into the subterranean formation. For instance, drilling operations play an important role when developing oil, gas or water wells or when mining for minerals and the like. During the drilling operations, a drill bit passes through various layers of earth strata as it descends to a desired depth. Drilling fluids are commonly employed during the drilling operations and perform several important functions including, but not limited to, removing the cuttings from the well to the surface, controlling formation pressures, sealing permeable formations, minimizing formation damage, and cooling and lubricating the drill bit.
Properties of the drilling fluid are typically monitored during drilling operations. For instance, it is often desirable to accurately measure hydrocarbon gas concentrations of the drilling fluid as it leaves the well bore. The level of the hydrocarbon gas in the drilling fluid may affect how the well is to be drilled as well as the safety of the drilling rig and personnel involved. Moreover, the concentration of hydrocarbon gases and other components present in the drilling fluid may be indicative of the characteristics of the formation being drilled and the drilling environment. Accordingly, the analysis of drilling fluids and the changes they undergo during drilling operations may be important to the methods of drilling as well as the efficiency of the drilling operations. Consequently, during drilling, completion and testing of a wellbore, it is desirable to obtain analytical measurements of the fluids that are returned to the surface from the well bore.
One proposed method for collecting and analyzing the drilling fluid involves submerging a rotor within a vessel into the drilling fluid as the drilling fluid exits the wellbore. Typically, the placement of this “gas trap” is in an open pit or header box which is exposed to atmospheric conditions. The drilling fluid is agitated as it enters into and exits out of the vessel and some of the gasses dissolved therein evaporate and escape the confines of the fluid. These vaporized gases are then collected and processed by analytical methods to determine the presence and levels of hydrocarbons and other components in the drilling fluid.
There are currently various conventional methods for collection of gaseous samples for analytical processing during drilling operations. One method entails attaching the sample point to the primary fluid/gas separator near the atmospheric end of the manifold system. However, by the time the gas from the well bore has entered the large volume of this separator it has typically become less significant as it has already undergone mixing with other gases and lag separation from the fluids from which it was derived. Other methods entail collecting an amount of drilling fluid before the separator and processing the drilling fluid to extract any gaseous compounds that are dissolved therein. Because the sampling in the second method occurs in the main stream of fluid from the well, it will not be compromised by the mixing of any other atmospheric gases or be separated from lag by any other process. However, this method does not allow an efficient continuous sampling of the drilling fluids.
Thus, most method for collection of gaseous samples for analytical processing during drilling operations generally require some way of accounting for lag time in the well bore and efficiency of the sampling method in order to provide accurate information regarding the composition and location hydrocarbons and other fluids downhole. Conventional methods may utilize standard correction factors to account for efficiency of the gas extractor; however, such correction factors may not accurately reflect the efficiency of a particular system.